The long-term objective of this study is to develop strategies for the prevention of osteoporosis in black women. Most studies have excluded racial minorities to limit extraneous variation. However, the number of black women over 65 years of age is increasing rapidly. An increase in longevity of 5-6 years is expected to cause a doubling of incidence rates. A comprehensive model for involutional loss of body cell mass and bone mass developed for white women, and strategies for prevention of osteoporosis, must be developed for bone loss in minority women. Body cell mass and adiposity are increased black compared to white Americans; the relationship of these increased black compared to white Americans; the relationship of these compartments to skeletal mass and body cell mass are higher in black women, the pattern of involutional loss is similar in blacks and whites. WE further hypothesize that the determinants of bone loss are similar among racial groups and that there is an accelerated loss of body cell mass and skeletal mass following menopause. In this protocol, a cross sectional study of body cell mass, fat, and skeletal mass in 300 normal black women aged 20-80, shall include total body calcium total body potassium, fat, and body fat, and bone mineral density of the radius, proximal femur and lumbar spine. In addition, annual measurement will be performed on 60 women in the 30-40-year and 5-60-year age cohorts. The specific aims are to 1) develop a comprehensive description of aging loss from the total skeleton, the radius, spine and femur; 2) determine the relative influence of peak bone mass and subsequent bone loss on the development of low bone mass; 3) examine the relationship of the loss of body cell mass, skeletal mass, and fat; 4) characterize the determinants of bone loss in various stages of the life cycle. The information derived from this study will provide comprehensive normative data that may be used for evaluation of bone mineral measurement in black women. The similarity or difference from previous studies in white women will suggest the strategies for prevention of bone loss that should be tested.